The present invention relates to an imprinting apparatus for transferring an uneven pattern with protrusions and recesses of a stamper to be replicated on a recording medium substrate, such as a magnetic recording medium, by pressing the stamper onto a resist layer or a polymer layer applied on the substrate.
With increasing recording density of a magnetic recording medium for use in a hard disk drive, micro machining technologies have been proposed including electron beam lithography, focused ion beam lithography, and nano imprinting lithography for manufacturing discrete track media and bit patterned media. In the nano imprinting lithography technology, as shown in U.S. Pat. No. 5,772,905, a stamper having a pattern of protrusions and recesses formed thereon is pressed onto a resist surface of a recording medium substrate to perform pattern transfer. This technology can carry out pattern transfer of a full surface of a magnetic recording medium at one time of pressing with a stamper to achieve high throughput production of magnetic recording media.
The nano imprinting lithography technology includes a 2P method, a hot embossing method, and a high pressure pressing method. The high pressure pressing method, which can perform pattern transfer with high precision and with high throughput, uses an imprinting apparatus as shown in Japanese Unexamined Patent Application Publication No. 2005-108351.
The imprinting apparatus comprises principal components of a press bottom plate with a surface for mounting a substrate having a resist film thereon and a press top board having a stamper with a disk shape and disposed allowing movement to approach and depart relative to the press bottom plate. The stamper has a pattern of protrusions and recesses in the central area thereof representing recording data.
In this structure, when the stamper is pressed onto a resist layer or a polymer layer formed on a recording surface of a magnetic recording medium substrate, the resist layer flows along the pattern of the stamper to transfer the pattern of protrusions and recesses on the recording surface of the substrate.
When a release agent is applied on a surface of the stamper, the release agent is gradually peeled off due to repeated transfer processes causing regional variation in the releasing effect. In this situation, the resist layer has a regional variation in a film thickness thereof and a quantity of resist flowing to the pattern is microscopically different from place to place. For this reason, an adhesive force between a recording surface and a stamper may differ from an adhesive force between another recording surface and another stamper. As a result, in the process of releasing the substrate from the stampers, the substrate is apt to be hardly released from the stamper in the side of the larger adhesive force, and the positions of holding the substrate are unstable in the die in the movable side and the die in the fixed side. As a consequence, when the substrate after the transfer process is taken out by means of a handler of a transporting robot, for example, the handler must have a rather complicated structure because the handler needs to cope with a plurality of positions for taking out the substrate. If the substrate has adhered to the upper stamper, it may falls down and be damaged. Regarding this problem, it is generally desired to hold the substrate always on the lower side die.
In view of the requirement, Japanese Unexamined Patent Application Publication No. 2008-012859 has proposed an imprinting device provided with a release pin for releasing the stamper from a recording surface of a magnetic recording medium substrate after the transfer process. The release pin having a releasing portion is disposed in a center holes of the substrate and of one of the stamper and moved in the radial direction of the stamper and also moved in the vertical direction by a driving device. One of the two stampers made of quarts is applied with optically curing resin on one side of the stamper. The magnetic recording medium substrate is also applied with optically curing resin on one side thereof.
In this structure, the magnetic recording medium substrate is disposed between the two stampers each supported by an upper plate and a lower plate and pressed. Then, ultraviolet light beam is irradiated in this pressed condition. After the optically curing resin is cured, the upper and lower plates are brought apart from each other allowing the magnetic recording medium substrate having the patterns of the stampers transferred on both surfaces of the substrate to be extracted. In this process, the releasing portion of the release pin mentioned above is brought into contact with beveling parts of the stamper and of the substrate and moved upwards. By this operation, one of the stampers is peeled off from one of the recording surfaces of the substrate. The releasing portion of the release pin is then moved downwards and brought into contact with beveling parts of the other stamper and of the substrate and moved yet downwards. Thus, the other stamper is bent and released from the other recording surface of the substrate, producing a magnetic recording medium substrate with the patterns transferred on the both surfaces thereof.
Particles may be generated in the imprinting device at a bearing part between an upper plate or a lower plate and a guide member for guiding the upper plate or the lower plate, the guide member being provided in a lifting mechanism for the upper or lower plate. If the particles are floating and attached onto the pattern of protrusions and recesses of the stamper representing recording data, the pattern defects due to the particles may be transferred onto the recording surface of the substrate. Hence, the atmosphere in the imprinting device must be kept clean.
The imprinting device disclosed in Japanese Unexamined Patent Application Publication No. 2008-012859 Patent Document 3 is provided with a release means for releasing the stamper from the recording surface of the magnetic recording medium substrate. This structure is significantly effective in view of mass production of magnetic recording medium substrates.
It is not easy, however, to control precisely and quickly the operation of a driving device so that the tip of the releasing portion of the release pin is brought into contact with the beveling parts of the relatively thin stamper and the substrate. This situation inhibits high throughput production of magnetic recording media using the imprinting device.
In addition, there exists no imprinting device that has a construction considering cleanliness in the device.
In view of the above problems, it would be desirable to provide an imprinting apparatus for transferring a pattern of protrusions and recesses on a nano imprinting stamper to a recording medium substrate of a magnetic recording medium or the like by pressing the stamper onto a resist layer or a polymer layer applied on the substrate, wherein the substrate, after the transfer process, can be removed from the stamper easily and quickly, and further, a clean atmosphere in the imprinting apparatus can be kept.